Ferroelectric memories (FeRAMs) that use polarization reversal of a ferroelectric material to hold information in a ferroelectric capacitor structure are being developed today. Ferroelectric memories are especially drawing attention because they are non-volatile memories that do not lose information held in them when power is removed from them, can be integrated with high density, are driven at high speed, highly durable, and consume low power.
The ferroelectric film of the ferroelectric capacitor structure is typically made of a ferroelectric oxide having a perovskite crystalline structure, such as a PZT (Pb(Zr,Ti)O3) film or SBT (SrBi2Ta2O9) film, having a large remnant polarization, for example approximately 10 (μC/cm2) to approximately 30 (μC/cm2).    Patent document 1: Japanese Patent Application Laid-Open No. 2000-91516    Patent document 2: Japanese Patent Application Laid-Open No. Hei. 01-214126    Patent document 3: Japanese Patent Application Laid-Open No. Hei. 07-135203    Patent document 4: Japanese Patent Application Laid-Open No. Hei. 03-195025